一个xft2的小问题

alessandro

看有很多关于xft2的文章，可我还不太清楚这个xft2是个什么东西，麻烦给解释一下。

euboy

The current version of Xft (2.0) provides a client-side font API for X applications. It uses Fontconfig to select fonts and the X protocol for rendering them. When available, Xft uses the Render extension to accelerate text drawing. When Render is not available, Xft uses the core protocol to draw client-side glyphs. This provides completely compatible support of client-side fonts for all X servers.

Drawing anti-aliased text with the core protocol involves fetching pixels from the destination, merging in the glyphs and shipping them back. This can be a performance problem when the latency between client and server is high. Drawing non-AA text with the core protocol can be done by just sending the glyphs from the client to the server. This eliminates any latency effects and makes rendering speed depend only on bandwidth. Careful protocol selection can make the bandwidth scale linearly with the pixel size of the glyphs, so performance is acceptable, even with relatively large glyphs.

When using legacy X servers (those without Render support) across a network, disabling anti-aliased text will improve text performance so that applications are reasonably usable even if completely dependent on client-side fonts.